For example, as shown in FIG. 8, a seat cushion frame for a vehicle is generally composed of a frame 101 for a seat cushion and a frame 102 for a seat back connected thereto (for example, JP-A-2004-338632). A conventional seat cushion frame for a vehicle is formed mainly as a steel sheet metal construction, and a resin seat cushion frame substantially does not exist. Therefore, in the conventional structure, there is a limit in decreasing the weight of the seat cushion frame for a vehicle.
Further, for a seat cushion frame for a vehicle, there is a mechanism that prevents a front section of the seat cushion frame from excessively sinking (hereinafter, also referred to as a submarine prevention mechanism) is required to be provided to protect a passenger at the time of a collision, etc. For example, in JP '632, as shown in FIG. 8, a submarine prevention mechanism 103 having a complicated structure, separate from the seat cushion frame 102, is provided.
Furthermore, in a conventional steel seat cushion frame, although as the entire frame it is formed as a structure having a C-shaped planar shape opening to the rear side (the rear side of a seat), respective structural sections are manufactured as components separate from each other and it is structured by connecting them to each other.
As described above, because a conventional seat cushion frame for a vehicle is composed of steel, the weight is great, there is a limit in reducing the weight while securing a rigidity required for the entire seat cushion frame and, therefore, it is difficult to greatly reduce the weight.
Further, when a submarine prevention mechanism is attached, because a complicated mechanism is attached as a component separate from the seat cushion frame, the number of components increases and the structure as a whole also becomes complicated.
Furthermore, because a conventional seat cushion frame for a vehicle is structured by connecting respective structural members manufactured as components separate from each other, the number of components is great, and many operations are required for the assembly.
Accordingly, paying attention to such problems in the conventional seat cushion frame for a vehicle, it could be helpful to provide a seat cushion frame for a vehicle in which a great lightening in weight can be achieved by changing the raw material of the main structural component to a resin, and in which decreasing the number of components and simplification of the overall structure can be achieved in consideration of providing a submarine prevention function.
Further, it could be helpful to provide a seat cushion frame for a vehicle which, even if the raw material of the main structural component is changed to a resin, can secure sufficiently high rigidity and strength, and which can be easily manufactured.